Yubidenwa is an app that makes your iPhone/iPad speak on your behalf when you are in a no-talk situation or if you have speech difficulties. Type a text on the fly or get Yubidenwa to say it by tapping one of your custom words or sentences. You can even manage entire conversations this way. There is a series of apps and hardwares of Yubidenwa. Here is a web site of Yubidenwa in Japan. (Japanese only)